PEOCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 407 



The radiila has a large flat, ovate central tooth with a thicketiecl an- 

 terior edge but no marked cusp ; on each side of this two rhomboidal 

 flat laterals with a similarly thickened anterior margin, the inner is the 

 larger and the outer somewhat more rounded in form; close to this are 

 two minute narrow laterals with small cusps, hidden i)arL]y under the 

 cusps of the next or major lateral, for which reason thej' cannot well be 

 made out until the radula is partly torn apart or broken up; these two 

 little laterals are the most anterior of the transverse series, which has a 

 form like a very transverse M ; the major lateral has strong Docoglos- 

 sate features, being set on a flat plate whose posterior inner and anterior 

 outer corners are thickened and raised into the likeness of a pseudo- 

 cusp, the true shaft of the tooth being very short and terminating in a 

 strong tridentate pellucid cusp; the outer tooth is a squarish, plate-like 

 uncinus, exactly as in some chitons, with a thickened longitudinal ridge 

 near the inner margin. 



Length of shell about 10.0; width 7.5, and altitude 4.0™". 



Dredged by the United States Fi'sli Commission in 1881 at stations 

 023, 940, and 950 in 96, 130, and G9 fathoms, sandy bottom, about 75 miles 

 S. and W. from Martha's Vineyard. Bottom temperature 52°, which, 

 belongs to the warmer bottom area. This very remarkable form would 

 have been called a " synthetic type" by Prof. Louis Agassiz. The shell 

 at once recalls Capulacmcca { = Filidium Midd.), which, however, is dis- 

 tinctively Taenioglossate in dentition. The details of the -branchial 

 leaves resemble those in Patella, the position of the branchite and the 

 form of the head resemble Acmoea, the smooth thick mantle margin and 

 absence of eyes are characters found in Lepetidw. Some features in the 

 dentition recall Chitonidw, and others Cocculinidw. The position of the 

 animal in its shell is as in the Rhiphidoglossa universally. 



Nothing of the kind has been recognized in the collection made by 

 Messrs. Sigsbee and Bartlett, of the U. S. Xavy, in the Gulf of Mexico and 

 Antilles, under the supervision of Prof. Alex. Agassiz, on the United 

 States Coast Survey steamer Blake, leading to the supposition that this 

 may be a rather more northern form, though found in the warm area. 



Order DOCOGLOSSA. 

 Stiborder ABRANCHIATA. 

 Animal destitute of external branchiae. Embryonic shell spiral. 

 Family LEPETID.E Gray. 



Lepetidce (Gray) Dall. Ann. Mag. of Nat. Hist, vii, pp. 286-291, April. 



Subfamily LEPETIN^. 



Animal without eyes, without lateral teeth, with a rhachidian tooth, 

 and erect uncini; muzzle with an entire margin, which is extended back- 



